Sample size

• 1. SAMPLE SIZE/CED 246/092314SAMPLE SIZECED 246-Evaluation in RuralDevelopmentANNA MERLINNA T. FONTANILLAMS DEVCOM, 1998-38359

2. SAMPLE SIZE/CED 246/092314Whats in this presentation Introduction What is a SAMPLE? Determining/selecting a sample Other sampling strategies Using formulas to determine samplesize 3. SAMPLE SIZE/CED 246/092314IntroductionPhase I:Understandingyour programPhase II:Planning yourevaluationPhase III:Implementingyourevaluation Collecting data Analyzing Data ReportingResults 4. SAMPLE SIZE/CED 246/092314InformationIntroductionDATALimitationson ALLimportantvariablesSAMPLE 5. SAMPLE SIZE/CED 246/092314What is a SAMPLE? 6. SAMPLE SIZE/CED 246/092314Determining a sampleFactors affecting sample sizePurpose of thestudyPopulationsizePrecision levelor samplingerrorConfidencelevelDegree ofvariability 7. SAMPLE SIZE/CED 246/092314Determining a samplePROBABILITYSAMPLINGNON-PROBABILITYSAMPLINGNON-BIASED/based onchanceBIASED/based on chanceGeneralization Not really appropriateStatistical methods forresult analysisNot appropriate 8. SAMPLE SIZE/CED 246/092314Selecting a sample 9. SAMPLE SIZE/CED 246/092314Other strategiesCensusSample size ofsimilar studyPublishedtablesFormulas 10. SAMPLE SIZE/CED 246/092314SlovinsFormulan =(1 + 2)n, n0 = sample sizee, e2 = margin of errorN = population sizeCochransFormula0 =222 = abscissa of the normalcurve that cuts off an area at the tails = degree of variability = 1- 11. SAMPLE SIZE/CED 246/092314Finite populationcorrectionn =01 +(0 1)CochransFormula0 =22n, n0 = sample sizeN = population size 12. SAMPLE SIZE/CED 246/092314